In anther cultures of Solanum carolinense L., Murashige and Skoog's medium (MS) supplemented with 2.2 mg · l(-1) 2,4-dichlorophenoxyacetic acid (2,4-D) and 6.0 mg · l(-1) kinetin (KIN) served as callus induction medium. Cytological observations confirmed that the callus originated from pollen grains. Upon transfer to medium lacking 2,4-D, callus cultures regenerated shoots exclusively. However, maximum efficiency in regeneration occurred only after callus had been maintained in the presence of 2,4-D for a minimum of 12 weeks. Callus younger than this or older than 16 weeks showed a significant decline in organogenic competence when transferred to the appropriate medium. It is suggested that 2,4-D may establish a transitory potential for regeneration in pollen-derived callus cultures but must be removed before this potential can be expressed.